Machine for the automatic high-speed, high precision machining of small parts, even those having a complicated form

ABSTRACT

A machine for automatic, high-speed, high precision machining of small parts comprising a piece holding turntable having an intermittent rotary movement for transporting each piece from one work station to the next and a plurality of interchangeable work units having at least one drive motor to advance the tool and at least one motor for the rotation of the work movement of the tool, each unit being placed in correspondence with a work station and being able to carry out different machining operations simultaneously as the pieces arrive at the station.

United States Paten Buzzi 1 Mar. 19, 1974 1 MACHINE FOR THE AUTOMATIC2.429.938 10/1947 Mansfield 29/38 c HIGILSPEED, HIGH PRECISION 2,216,14110/1940 Sinclair 2,318,619 11/1943 Noel 29/38 C MACHINING OF SMALLPARTS, EVEN THOSE HAVING A COMPLICATED FORM Inventor: Ugo Buzzi, Agno,Switzerland Assignee: Albe S.A., Lugano, Switzerland Filed: Dec. 22,1971 Appl. No.: 210,808

[30] Foreign Application Priority Data Sept. 30, 1971 Switzerland14281/71 [52] US. Cl. 29/38 C, 408/45 [51] Int. Cl B23p 23/00 [58] Fieldof Search 29/33 J, 38 C; 408/45 [56] References Cited UNITED STATESPATENTS 3,304,596 2/1967 Weidauer 29/38 C Primary Examiner-Francis S.Husar 5 7] ABSTRACT A machine for automatic, high-speed, high precisionmachining of small parts comprising a piece holding turntable having anintermittent rotary movement for transporting each piece from one workstation to the next and a plurality of interchangeable work units havingat least one drive motor to advance the tool and at least one motor forthe rotation of the work movement of the tool, each unit being placed incorrespondence with a Work station and being able to carry out differentmachining operations simultaneously as the pieces arrive at the station.

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w- -e ar rOvATTORNEYS PATENTEUIAR 19 BM sum as 0F 10 INVENTOR ATTORNEYSMACHINE FOR THE AUTOMATIC HIGH-SPEED, HIGH PRECISION MACHINING OF SMALLPARTS, EVEN THOSE HAVING A COMPLICATED FORM The present invention isdirected to a machine for the automatic, high-speed, high precision,machining of small parts, especially those having a complicated form,such as electrical contacts, parts or pieces having similar or differentholes, millings, or threads.

The machine, comprises a piece holding turntable, having an intermittentrotatory movement for transporting each piece from one work-station tothe next one, and a plurality of work units, each placed incorrespondence with a station, and each to carry out simultaneously onthe pieces which are presented to it as they arrive, different machiningoperations, is characterized by the fact that:

said work units are of one single type, standardized and autonomous andtherefore interchangeable from one station to another;

each work unit has at least one electric driving motor for advancing ofthe tool to the piece at the work station and at least one electriccommand motor for powering the work movement of the tool, said commandmotor being removably attached to the tool; the movement of the variousmotors being mechanically independent of the intermittent movement ofthe piece holding table;

the speed of the various electric motors on all the units aresimultaneously variable by means of a single control;

the synchronism of the various operations, which might otherwise bealtered by slight differences in the speed of the various motors, can.be ensured by restoring the phase setting at the beginning of each workoperation.-

The enclosed drawings represent a preferred, nonlimitative realizationof the machine according to the present invention:

FIG. 1 is a schematic axial section of the machine of the invention;

FIG. 2 represents a lateral view partially sectioned of a work unit on alarger scale;

FIG. 3 represents a perspective view of a detail of the work unit;

FIG. 4 represents a cross section view of the same unit illustrated inFIG.3;

FIG. 5 represents a work unit fixed onto a support for horizontalmachining;

FIG. 6 represents a work unit fixed onto a support for verticalmachining;

FIG. 7 represents a work unit fixed onto a support for inclinedmachining;

FIG. 8 represents an exploded perspective view. of the particularsregarding the fixing of a work unit to the platform or table integralwith the frame of the machine;

FIG. 9 represents a perspective view of the mechanism operating therotation of the piece holding turn table;

FIG. 10 represents in cross section the mechanism for the rotation ofthe grippers which grasp the piece to be machined;

FIG. 11 represents a perspective view of the same mechanism;

FIG. 12 represents different embodiment of the work unit;

FIG. 13 represents a support which permits the simultaneous holding oftwo work units at a single station.

The machine comprises essentially (see FIGS. 1 and 9) a piece holdingtable 1 having a rotating intermittent motion, bearing at equal regulardistances of its periphery a certain number of piece holding grippers22'.

If, for example, the piece holding table has 12 grippers distributeduniformly at its periphery each one at an angular interval of 30, therewill be the same number (that is twelve) of work stations. There is awork unit 3, 3', etc., inside each station, fixed on a support 4, 4etc., and each one of these units carries out a specific machining onthe work piece.

It is obvious that while the work unit 3 is carrying out a specificmachining on the corresponding piece, for example a drilling operation,at the same time the following successive work unit carries out anothermachining, for example, a screwing operation, so that at the same timeat each step of the turn table 1, the various pieces undergo successivemachinings and at each revolution of the piece holding table 1 of a rawor crude piece enters and a finished one comes out.

The lower part 1' of the piece holding table contains all thekinematics, that is all the mechanism (FIG. 9) necessary to transmit toit the intermittent .motion, including the electric motor.

The frame of the machine bears the fixed platform 5 (FIG. 1) havingannular grooves, 6 onto which the units are mounted in correspondencewith the single work stations.

The upper part 76 of the machine is made of synthetic insulatingmaterial constituting of a cover containing the current distributingsystem for the various motors.

In the cover 76 are provided channels into which are insertedconductors, that is circular bars for the distribution of the current tothe sockets into which are fitted the plugs joined to the conductorswhich feed the various motors. Conductors are provided for the feedingof the servomotors 11 (FIG. 2) and also power operated spindles 8holding the tools, which can be of different types according to thepower and the working speed.

Said tool holding motor spindles 8 are removable with the tool fromtheir respective seats in order to provide more easily for thereplacement of the tool.

A first new characteristic of the machine according to the presentinvention is constituted by the fact that the' various work units 3, 3,etc., are of one standard and independent type and are thereforeinterchangeable from one station to another.

A second characteristic consists of the fact that each work unit 3, 3',etc., has (FIG. 2) electric drive motors 11 and 8; the first 11 alsocalled servomotors, able to control the feed movement of the tool, thesecond 8 being able to control the machining carried out by the tool onthe same unit. Motors 1 l and 8 are operated independently of theintermittent mechanical feed motion of the piece holding table 1. Inother words there is complete independence of the intermittent movementof the piece holding table 1 and the feed motion and machining of thetool carried by each work unit, and there is no mechanical restraintbetween the two.

Furthermore, there is no mechanical restraint between the tool-holdingspindle and the servomotor 11 which controls the feed motion.

An essential characteristic of the machine according to the invention isconstituted by the fact that the speeds of the servomotors 11 carried bythe various units 3 and 3 are simultaneously variable by means of asingle control.

The above mentioned motors 8 and 1 1 can be, for example, of thealternating current type, that is asynchronous or eventually alsosynchronous, or of a direct current type. In the former case(asynchronous or synchronous motors) the variations of their speeds isdetermined by varying the frequency of the alternating current whichfeeds them.

In this case the machine is provided with a suitable variable frequencyalternating-current generator which can simultaneously feed all themotors 11 and 8 of the various work units (3, 3' etc.). By varying thefrequency, one varies the speed of the said motors and therefore onevaries the whole machining time of the machine, and one increases orreduces the machining time of the machine itself.

In case one should use asynchronous motors which present a sliding ofthe rotor with respect to the stator and therefore a slight variation ofthe speed, it is foreseen that at the end of a working operation thesynchronism of various machining must be reestablished by restoring thephase setting, as will now be described in more details.

For direct current motors the speed is varied by varying the voltageapplied.

There now follows a detailed description of the realization of the workunit with reference to the drawings 2, 3 and 4. l

The work unit (FIG. 2) is composed of a small block 3 in which isincorporated the feed system of the tool holding motor spindle 8 whichruns on balls in the hole of the bush 9. The power operated spindleholding the tools is easily removable from the block and thus from thetool, by sliding the levers in order to permit the rapid change of thetool.

The block 3 can be fixed on various different supports 4, 4', 4" etc.(FIGS. 5, 6, 7) according to the machining to be carried out, as we willdescribe further on. The feed device of the motor spindle 8 consists ofa motor 11 (FIG. 2) (which we will call servomotor) which transmits themovement, through the worm screw 12 and the nut 13'to the camshaft 14(FIG. 3).

The cam 15 then transmits by a system of levers 16 the movement to themotor spindle 8 (FIG. 2).

In order to vary the machining time, as already mentioned, it isnecessary to vary the speed of rotation of the servomotor 11.

It is further necessary to take into account the fact that the differentunits placed in correspondence with the different stations of work mustWork synchronously, that is, all the cams 15 of the different work unitsmust carry out one turn at the same time. A small error is acceptable;the error itself however must not accumulate over several machinings,since otherwise the synchronism between the units themselves would belost. This happens particularly when the electric servomotors 11 aresynchronous.

The speed of the servomotors 1 1 if of alternatingcurrent, is varied, ashas been already mentioned, by varying the frequency of the feedcurrent.

The variable frequency is delivered by a known type of static generatorof frequencies (not shown), which combines two frequencies, a mainfrequency and one generated separately, and permits infinite variationof the resulting frequency and as a consequence infinite variation ofthe speed and machining times of the machine. The frequency generatorfeeds all the servomotors 11.

The servomotors, as said, are three-phase asynchronous motors and thoughthey are fed from the same generator it is clear that their rotation isnot completely synchronous. In fact there will be slight differences dueto the different loads (according to the machining to be carried out incorrespondence with one station) and friction, etc. For this reasonthere has been incorporated into the block 3 of each unit, a system forthe phase setting of all the units, which functions as follows:

On the camshaft 14 (FIG. 3) (which obviously carries out one rotationfor each machining) there is fixed a cam 17 on which the lever 18 comesto rest. The cam 17 has, at point 0 (which corresponds to the end of themachining), a shoulder 17 (FIG. 4).

During the rotation of the shaft 14 when the shoulder 17 comes to point0, the lever 18 which is preloaded by the spring 22 moves, and by meansof the magnet 19 opens the reed contact 20 (a known type of contactconsisting of two blades one of which is magnetic and is worked by anelectromagnet or magnet). A signal which marks the end of the workmachining for each unit is thus obtained. When the contacts 20 of allthe work units are open, this means that all the units situated at thevarious stations have reached point 0, that is, the end of theirmachining.

Obviously, given the possible asynchronism, there will be smalldifferences, in time when this 0" point is reached. That is, not all thecontacts will open at exactly the same instant. The frequency of thecurrent feeding the servomotors 11 must therefore be brought rapidly tozero and the relative phase inverted.

This is obtained by superimposing as has already been mentioned, twocomponent frequencies the main frequency and a separately generated one,and acting in such a way that the result of the two former are annuledand then the phase is inverted.

The servomotors 11 are, as a consequence, first rapidly braked andsubsequently inverted in the direction of their rotation.

The negative rotation (in an inverse sense) is limited to the shoulder17' of the cam 17 which blocks the shaft 14 and then the respectiveservomotor 11.

The step movement of the piece holding table 1 (FIG. 1) begins as soonas all the work units arrive at 0" (reed contacts open).

During the time in which the part carrying table 1 moves one step, theservomotors 11 are braked and subsequently, by means of negativerotation, they are set in phase for the next machining.

In other words, the servomotors 11 which have had a greater forwardmovement than the others have time to return to 0" by means of theinverse rotation. No time is therefore lost for the synchronisation.

In the case in which direct current motors are used, the speed variationis obtained by varying the feed voltage and the inversion of movement iscarried out by reducing such feed voltage to zero and inverting it.

The various work units 3, 3' can be fixed onto three different supports,namely on a support 4' (FIG. 5) for horizontal machinings; on a support4 for vertical machinings (FIG. 6); on a support 4" (FIG. 7) providedwith semi-circular vertical grooves 72 which permit inclined machiningsaccording to angles between the vertical and the horizontal.

The fixing of the work units 3, 3 etc., on respective supports 4, 4, 4"is obtained by the use of the nuts 50 (FIG. 5).

The supports 4, 4, 4" are fixed by means of stirrups 51 (FIGS. 5 and 8)and tie rods 52 to the intermediate plate 53. The said intermediateplate 53 is, finally, fixed to the fixed platform 5 (FIGS. 1, 5, 8) bymeans of clamps 53 (FIGS. 5 and 8) which in their turn insert intoT-slots 6 of the platform 5. On the platform 5 there are holes 54 (FIG.8) in correspondence with each station.

There can be fixed into these holes, by means of pins or plugs 56, rods57 which act as leads guides to the intermediate plate 53 and facilitatethe regulation of the work unit 3' placed above, in particular forradial machinings, that is machinings whose axis is turned towards thecentre of the machine. For machining operations whose direction is notfacing towards the centre of the machine, the rods 57 can be removed andthe supports 4, 4, 4" of the work units 3, 3, 3" etc., can be fixed inany direction on the platform 5.

As can be seen from the drawing, the platform 5 has three T-slotsindicated by 6. This allows the fixing of the intermediate plate 53 notonly in the two middle and internal slots 6, 6, but also in the twomiddle and external slots 6, 6" thus allowing a much larger workingfield.

Thus each work unit can be moved and controlled: in a radial direction,that is towards the centre of the machine, by slightly loosening thefour fixing screws 65 (FIG. 8) of the base plate 53 and acting upon theradial macrometrical screw 60; in the lateral (tangential) direction byloosening the nut 61 of the tie-rod- 52 and acting of the micrometricscrew 63 (relative movement between plate and support); in heightloosening the three nuts 50 (FIG. 5) and acting on the micrometric screw64 (FIG. 6).

As regards the rotation movements of the turntable 1 (FIG. 1), the motor30 (FIG. 9) controls by means of the worm screw 31 and the gear 32 theshaft 33. On the shaft 33 is fixed the cam 34, which is in the form of aworm.

The cam 34 acts on the rollers 35 fixed on the disc 36 integral andcoaxial to the turntable 1. At each turn of the shaft 33 the cam 34produces a displacement of the turntable equal to the pitch of the cam34. The form of the cam 34 is such as to produce the movement of theturntable 1 by a fraction of a turn with constant acceleration anddeceleration. The cam 37 also integral with the shaft 33 controls, bymeans of the lever 38, the piston 39 whose conical extremity 39' aftereach movement (fraction of turn) of the table 1 is introduced into thecomplementary conical hole 80 and thus exactly fixes the position of theturntable itself. In other words, a part of the angular movement of theshaft 33 during a turn of the shaft itself is used to control therotation of the table 1, the remaining angular part for the indexing,that is the exact fixing of the table 1 in the position reached.

In the drawings 10 and l l the mechanism for the rotation of theself-centering grippers which grasp the piece to be machined is shown.The piece holding table 1 has a plurality of pans or plates 40 bearingthe grippers 2 (in FIG. 10 is shown an example of a-pair of grippers 2,but in the same holding pan 40 it is possible to provide other systemsof grippers). The pans 40 can be rotated by a certain angle passing fromone work station to another and this simultaneously to the angularmovement of the piece holding table 1.

During the machining time each pincer holding pan 40 is held fixedly byits respective anchoring lever 41 (FIG. 11) which with its taperedextremity penetrates into the complementary cavity 42 of the pan itself;said lever 41 rests at its other extremity on the cam 48 shaped in sucha way that when the piece carrying table 1 begins to move, the freeingof the lever 41 from the cavity 42 occurs, thus freeing the pan 40 ofeach unit. At the same time the disc 43, integral to the axis of theholding pan 40 comes into contact with the elastic blades 44, fixed tothe frame which holds the table 1 and by friction causes the rotation ofthe pan 40.

The lever 41 which had previously freed the pan 40, before the end ofone movement of the table 1 again stops the same pan in the desiredposition.

In one and the same carrying pan can be fixed more discs 43 of differentdiameters shown in 43 (FIG. 10) and which comes into contact with blades44' moved vertically with respect to the blades 44. It is thus possibleto obtain different rotation ratios of the pan 40- In this manner it ispossible to make the rotation of the pan perfect, in the sense thatchanging the ratios according to the angle of rotation required it ispossible to begin or terminate the rotation of the pan 40 always at thebeginning and at the end of the movement of the table 1, that is, whenthe moving speed of the table 1 is practically zero.

Furthermore it is possible to be able to rotate a gripper through acertain angle (for example between one work position and another andthrough another angle (for example between another work position and thesuccessive one.

Another type of work unit is represented in FIG. 12. It enables theimposing on the spindle of the tool holders two movements, one verticaland one horizontal.

The horizontal and vertical movements are controlled by two cams 68integral to the same axis 67 of a servomotor 11 as for the work unitillustrate in FIG. 2.

,The vertical movement is transmitted to the spindle throughparallelogram leverage 70 in such a way that this movement isindependent of the horizontal movement.

The parallelogram allows the motor to be moved vertically by means of acam independently of the position in which it is to be found.

Finally, in FIG. 13 there is provided a support 71 which allows two workunits to be held and as a consequence enables two operations to becarried out (one in a horizontal position and the other in a verticalone) simultaneously at the same station.

As regards the general working of the machine, and in particular thesynchronisation of the work units with the control of the piece holdingturntable 1, the following is to be made clear: when all the work unitsarrive at point 0, the motor 30 (FIG. 9) which controls the rotation ofthe turntable is switched on and the shaft 33 carries out a rotation. Acontact 45 gives the position of the shaft 33. When the rotation hasfinished, the work units are synchronized, and are ready to receive thecommand to carry out a work cycle, and so on.

I claim:

1. In a machine for the automatic, high-speed, highprecision machiningof small parts of complicated form, comprising a piece-holding table; aplurality of work stations around said table; means for intermittentlyrotating said table to transport each piece from one work station to thenext; and a plurality of work units, each in correspondence with a workstation and each operable to carry out simultaneously on the pieceswhich are presented to them a different machining operation, said workunits being of a single type and interchangeable from one work stationto another; each work unit having a tool, a feeding means for movingsaid tool from an initial starting position to a position where the toolworks on said piece transported to said work station, said feeding meansbeing powered by an electric feed motor, an electric command motor forsupplying power to the tool, said command motor being removably attachedto the tool, the feeding movement of the tool being mechanicallyindependent of the intermittent movement of the piece-holding table, theimprovement which comprises:

a. a single control means for simultaneously varying the speed of theelectric feed motors,

b. resetting means for resetting all of the tools to said initialstarting positions at the end of each machining operation comprisingbrake means for braking said feed motors at the end of each machiningoperation, reversing means for rotating the feed motors in a reversedirection after operation of said brake means and stop means forstopping the reverse rotation of said feed motors when said feed motorshave moved said tools to said initial starting positions; and

c. means for starting all of said feed motors at the same time after allof the tools are reset to said initial starting positions.

2. The machine according to claim 1, wherein said stop means comprises acam rotated by said feed motor and electric switch means operated bysaid cam to stop said reverse rotation of said feed motor when the toolis moved to said initial starting position.

1. In a machine for the automatic, high-speed, high-precision machiningof small parts of complicated form, comprising a pieceholding table; aplurality of work stations around said table; means for intermittentlyrotating said table to transport each piece from one work station to thenext; and a plurality of work units, each in correspondence with a workstation and each operable to carry out simultaneously on the pieceswhich are presented to them a different machining operation, said workunits being of a single type and interchangeable from one work stationto another; each work unit having a tool, a feeding means for movingsaid tool from an initial starting position to a position where the toolworks on said piece transported to said work station, said feeding meansbeing powered by an electric feed motor, an electric command motor forsupplying power to the tool, said command motor being removably attachedto the tool, the feeding movement of the tool being mechanicallyindependent of the intermittent movement of the piece-holding table, theimprovement which comprises: a. a single control means forsimultaneously varying the speed of the electric feed motors, b.resetting means for resetting all of the tools to said initial startingpositions at the end of each machining operation comprising brake meansfor braking said feed motors at the end of each machining operation,reversing means for rotating the feed motors in a reverse directionafter operation of said brake means and stop means for stopping thereverse rotation of said feed motors when said feed motors have movedsaid tools to said initial starting positions; and c. means for startingall of said feed motors at the same time after all of the tools arereset to said initial starting positions.
 2. The machine according toclaim 1, wherein said stop means comprises a cam rotated by said feedmotor and electric switch means operated by said cam to stop saidreverse rotation of said feed motor when the tool is moved to saidinitial starting position.